1. Field of the Invention
The present invention relates to a ballast. More specifically, the present invention relates to a ballast that can save the use of internal connection terminals.
2. Descriptions of the Related Art
Lamps have been used in more and more widespread applications since the advent thereof. One of the most widespread and well-known applications is lighting. As people are looking for better lighting qualities, a lighting equipment is usually equipped with many lamps rather than one lamp.
FIG. 1 illustrates a schematic diagram of the conventional ballast 1 comprising a plurality of lamps. The ballast 1 comprises a first lamp set 11, a second lamp set 13, a switch circuit, and direct current (DC) input terminals 171, 172. The switch circuit comprises capacitors 151, 152 and switches e.g. Mosfet 153, 154. The first lamp set 11 comprises a resonant circuit 111, a plurality of preheat circuits 112, 113, 114, and a plurality of lamps 115, 116. The second lamp set 13 comprises a resonant circuit 131, a plurality of preheat circuits 132, 133, 134, and a plurality of lamps 135, 136. Uses and functionalities of the elements of the ballast 1 are well known to those skilled in the art, thus only those relevant to the present invention will be described herein.
The first lamp set 11 and the second lamp set 13 are connected in parallel. A filament of the lamp 116 of the first lamp set 11 is connected to a filament of the lamp 136 of the second lamp set 13 at a node 14, and the node 14 can be considered as a junction for parallel connection. FIG. 2 illustrates connections between the lamps 116, 136 and internal/output (I/O) terminals of the ballast 1. Particularly, connection wires 12a, 12b, 12c, 12d, 12e are required for the connection of the lamps 116, 136 within the ballast 1. Meantime, nine I/O terminals (i.e. the nine blocks with small circle in FIG. 2) and connection wires 11a, 11b, 11c are further required for connection with the ballast. Such complex connections inevitably increase manufacturing cost of and space occupation within the ballast 1.
In summary, efforts still have to be made in the art to provide a ballast that can save the use of internal connection terminals, wires, and internal space.